Furnace with O.E. thermostat

Preston · 05-13-2012, 10:48 PM

My original thermostat has a/c with hi/lo then fan then heat the other switch is auto and on for blower. The auto selection with the other switch on a/c blows only when a/c turns on and off. When the other switch is on on the blower blows all the time and a/c cycles on and off. My question is the heat setting and the other switch on auto works but if it is on heat and on instead of auto, the furnace doesn't come on or blow. Is it supposed to?

Quahog · 05-14-2012, 05:34 AM

Preston, I'm not sure I understand your question but I will give it a try. Most thermostats that I have seen have Cool /Heat on one switch and Auto / Fan on the other. If you set it to Fan, the blower motor runs constantly, whereas in Auto, it will cycle when either the AC or Furnace comes on.

Your original having High/Low gives you some additional control, which is why you see folks adding a micro switch to their installs when changing out the thermostat for a digital model.

Preston · 05-14-2012, 07:34 PM

Quote:

Originally Posted by Quahog

Preston, I'm not sure I understand your question but I will give it a try. Most thermostats that I have seen have Cool /Heat on one switch and Auto / Fan on the other. If you set it to Fan, the blower motor runs constantly, whereas in Auto, it will cycle when either the AC or Furnace comes on.

Your original having High/Low gives you some additional control, which is why you see folks adding a micro switch to their installs when changing out the thermostat for a digital model.

Give it one more try lol. If I have heat and auto selected it works, if I have heat and on selected nothing happens. For the a/c if you select cool and auto it (being the compressor and blower) all turns on and off together. If setting is cool and on (instead of auto) the fan runs all the time and compressor cycles on and off but fan runs all the time just like in my house. It just doesn't work the same with heat.

Quahog · 05-15-2012, 04:27 AM

From your description, the AC side is working correctly. When you say "if I have heat and on selected nothing happens.", are you saying the blower doesn't come on at all? If that's the case, I'd troubleshoot that. Seems to me like on the furnace side, the blower motor comes in for 15 seconds or so before the burner ignites. If that were absent, it might explain why the furnace doesn't come on while in "on" vs. "auto".

Preston · 05-15-2012, 04:39 AM

Ok, I'll check into it further then. I just wasn't sure if you could make the blower run all the time and the heat cycle on and off.

rwstinson · 08-10-2012, 09:17 PM

Fan should work in auto and on with A/C. This circulates air. Auto only would be for furnace. I don't want air moving in 40degree temp without the furnace warming the air.

bubba1170 · 08-10-2012, 11:26 PM

I have a challenge that I need assistance with. Sorry to hi jack the thread.

I just got our rig out of storage to prep it for a trip. I've always been told to start the fan on low first and run it for a little while then kick the A/C on and eventually into high. Well my challenge is the fan works fine but when I kick the A/C on the fan drops to a very low speed and eventually trips either the breaker in the rig or the breaker on the house. What am I doing wrong or what's the issue.

Thanks,
Brian

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